1. Technical Field
The present disclosure relates to a damper based on carbon nanotubes, and a loudspeaker using the same.
2. Description of Related Art
A loudspeaker is an acoustic device transforming received electric signals into sounds. The electric signals have enough power to make the sounds audible to humans. There are different types of loudspeakers that can be categorized by their working principle, such as electro-dynamic loudspeakers, electromagnetic loudspeakers, electrostatic loudspeakers and piezoelectric loudspeakers. Among the various types, electro-dynamic loudspeakers have simple structures, good sound quality, and low cost, thus it is most widely used.
Electro-dynamic loudspeakers typically include a diaphragm, a bobbin, a voice coil, a damper, a magnet, and a frame. The voice coil is an electrical conductor, and is placed in the magnetic field of the magnet. By applying an electrical current to the voice coil, a mechanical vibration of the diaphragm is produced due to the interaction between the electromagnetic field produced by the voice coil and the magnetic field of the magnets to produce sound waves.
To evaluate the loudspeaker, a sound volume is a decisive factor. The sound volume of the loudspeaker relates to the input power of the electric signals and the conversion efficiency of the energy (e.g., the conversion efficiency of the electrical to sound). The larger the input power, the larger the conversion efficiency of the energy and sound volume of the loudspeaker. However, when the input power is increased to certain levels, the damper and diaphragm could deform or even break, thereby causing audible distortion. Therefore, the strength of the elements in the loudspeaker affect a rated power of the loudspeaker. The rated power is the highest input power the loudspeaker can produce sound without the audible distortion. Additionally, the lighter the weight of the elements in the loudspeaker, such as the weight of the damper and the weight per unit area of the diaphragm, the smaller the energy required for vibrating the diaphragm, and the higher the energy conversion efficiency of the loudspeaker, and sound volume produced by the same input power. Thus, the strength and the weight of the damper are important factors affecting the sound volume of the loudspeaker. The weight of the damper is related to a thickness and a density thereof. Accordingly, the higher the specific strength (e.g., strength-to-density ratio), the thinner the damper of the loudspeaker, and the higher the sound volume of the loudspeaker.
However, in prior art, the damper is usually made of pure cotton or blended fabric. The rated power of conventional loudspeakers is difficult to increase because of the conventional material of the damper. In general, the rated power of a small sized loudspeaker is only 0.3 watt (W) to 0.5 W. A larger bobbin thickness to achieve a larger specific strength, results in a greater damper weight. Thereby, it is hard to improve the energy conversion efficiency of the loudspeaker. Therefore, to increase the rated power and the energy conversion efficiency of the loudspeaker and to increase sound volume, the improvement of the loudspeaker is focusing on increasing the specific strength and the decreasing of the weight of the damper.
What is needed, therefore, is a damper with high specific strength and light weight and a loudspeaker using the same.